Nowadays,the increasing electromagnetic waves generated by wearable devices are becoming an emerging issue for human health,so stretchable electromagnetic interference(EMI)shielding materials are highly demanded.Eleph...Nowadays,the increasing electromagnetic waves generated by wearable devices are becoming an emerging issue for human health,so stretchable electromagnetic interference(EMI)shielding materials are highly demanded.Elephant trunks are capable of grabbing fragile vegetation and tearing trees thanks not only to their muscles but also to their folded skins.Inspired by the wrinkled skin of the elephant trunks,herein,we propose a winkled conductive film based on single-walled carbon nanotubes(SWCNTs)for multifunctional EMI applications.The conductive film has a sandwich structure,which was prepared by coating SWCNTs on both sides of the stretched elastic latex cylindrical substrate.The shrinking-induced winkled conductive network could withstand up to 200%tensile strain.Typically,when the stretching direction is parallel to the polarization direction of the electric field,the total EMI shielding effectiveness could surprisingly increase from 38.4 to 52.7 dB at 200%tensile strain.It is mainly contributed by the increased connection of the SWCNTs.In addition,the film also has good Joule heating performance at several voltages,capable of releasing pains in injured joints.This unique property makes it possible for strain-adjustable multifunctional EMI shielding and wearable thermotherapy applications.展开更多
Microwave absorbers with unique optical and mechanical performance are urgent for complex electromagnetic environment.Here,we demonstrate the mechanically flexible,optically transparent,and microwave-absorbing polyacr...Microwave absorbers with unique optical and mechanical performance are urgent for complex electromagnetic environment.Here,we demonstrate the mechanically flexible,optically transparent,and microwave-absorbing polyacrylamide(PAM)hydrogel,in which the polar water molecules with high polarization contribute to the efficient microwave attenuation,but the binding between water molecules and PAM will slow down the orientation polarization of polar molecules.Meanwhile,the dominated dielectric property of water molecules in PAM hydrogel determines that the molecules displacement in polymer mixture is feasible for manipulating permittivity.Besides,by decreasing temperature,the flexible and transparent hydrogel will switch to rigid and opaque state as the phase conversion between amorphous and polycrystal state.By constructing structures with such hydrogel,the obtained absorber also exhibits the optical and mechanical switchable properties,covering the effective absorption within 5.7-18 GHz.This work provides an effective method to fabricate optically and mechanically manipulable microwave absorbers for intelligent electromagnetic stealth systems.展开更多
Ultrafast fiber lasers are in great demand for various applications, such as optical communication, spectroscopy,biomedical diagnosis, and industrial fabrication. Here, we report the highly stable femtosecond pulse ge...Ultrafast fiber lasers are in great demand for various applications, such as optical communication, spectroscopy,biomedical diagnosis, and industrial fabrication. Here, we report the highly stable femtosecond pulse generation from a MXene mode-locked fiber laser. We have prepared the high-quality Ti_3C_2 T_x nanosheets via the etching method, and characterized their ultrafast dynamics and broadband nonlinear optical responses. The obvious intensity-and wavelength-dependent nonlinear responses have been observed and investigated. In addition, a highly stable femtosecond fiber laser with signal-to-noise ratio up to 70.7 dB and central wavelength of 1567.3 nm has been delivered. The study may provide some valuable design guidelines for the development of ultrafast, broadband nonlinear optical modulators, and open new avenues toward advanced photonic devices based on MXenes.展开更多
Oxidation protective MoSi2-MosSi3/SiC multi-coatings for carbon/carbon composites were prepared by chemical vapor reaction and slurry-sintering method. The influence of preparation technology on the structure and phas...Oxidation protective MoSi2-MosSi3/SiC multi-coatings for carbon/carbon composites were prepared by chemical vapor reaction and slurry-sintering method. The influence of preparation technology on the structure and phase composition of the coating was investigated by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS） and X-ray diffraction （XRD） analyses, and then their relationship was discussed. The results indicate that the Si/Mo ratio of the slurry and sintering processing were two main factors that significantly affected the structure and phase composition of the multi-coating. Appropriate sintering process and relatively high Si/Mo ratio were essential for preparing the multi-coating with dense structure and favorable phase composition. After being sintered at 1723 K for 2 h and with the Si/Mo ratio of the slurry being 4.5 （weight ratio）, a dense structure accompanied by favorable phase composition of the coating can be obtained. When heat treated at 2373 K for I h, this coating became more compact and continuous. Oxidation tests （performed at 1623 and 1823 K） demonstrated that both of these two obtained multi-coatings exhibited better anti-oxidation property than single layer SiC coating.展开更多
基金financially supported by the National Natural Science Foundation of China(52073302,52103311)Hunan Provincial Natural Science Foundation for Distinguished Young Scholars(No.14JJ1001).
文摘Nowadays,the increasing electromagnetic waves generated by wearable devices are becoming an emerging issue for human health,so stretchable electromagnetic interference(EMI)shielding materials are highly demanded.Elephant trunks are capable of grabbing fragile vegetation and tearing trees thanks not only to their muscles but also to their folded skins.Inspired by the wrinkled skin of the elephant trunks,herein,we propose a winkled conductive film based on single-walled carbon nanotubes(SWCNTs)for multifunctional EMI applications.The conductive film has a sandwich structure,which was prepared by coating SWCNTs on both sides of the stretched elastic latex cylindrical substrate.The shrinking-induced winkled conductive network could withstand up to 200%tensile strain.Typically,when the stretching direction is parallel to the polarization direction of the electric field,the total EMI shielding effectiveness could surprisingly increase from 38.4 to 52.7 dB at 200%tensile strain.It is mainly contributed by the increased connection of the SWCNTs.In addition,the film also has good Joule heating performance at several voltages,capable of releasing pains in injured joints.This unique property makes it possible for strain-adjustable multifunctional EMI shielding and wearable thermotherapy applications.
基金This work was financially supported by the National Natural Science Foundation of China(No.62101073)Natural Science Foundation of Hunan Province(Nos.2021JJ30154 and 2022JJ40127)+1 种基金Scientific Research Project of Hunan Provincial Education Department(No.21B0557)Development and Reform Commission of Hunan Province 2021 Innovative Research and Development Project(No.10:Preparation and Electromagnetic Properties of Biochar Composites).
文摘Microwave absorbers with unique optical and mechanical performance are urgent for complex electromagnetic environment.Here,we demonstrate the mechanically flexible,optically transparent,and microwave-absorbing polyacrylamide(PAM)hydrogel,in which the polar water molecules with high polarization contribute to the efficient microwave attenuation,but the binding between water molecules and PAM will slow down the orientation polarization of polar molecules.Meanwhile,the dominated dielectric property of water molecules in PAM hydrogel determines that the molecules displacement in polymer mixture is feasible for manipulating permittivity.Besides,by decreasing temperature,the flexible and transparent hydrogel will switch to rigid and opaque state as the phase conversion between amorphous and polycrystal state.By constructing structures with such hydrogel,the obtained absorber also exhibits the optical and mechanical switchable properties,covering the effective absorption within 5.7-18 GHz.This work provides an effective method to fabricate optically and mechanically manipulable microwave absorbers for intelligent electromagnetic stealth systems.
基金National Natural Science Foundation of China(NSFC)(11574079,61475102,61775056)Natural Science Foundation of Hunan Province(2017JJ1013)Ministry of Education of the People’s Republic of China(MOE)(6141A02033404)
文摘Ultrafast fiber lasers are in great demand for various applications, such as optical communication, spectroscopy,biomedical diagnosis, and industrial fabrication. Here, we report the highly stable femtosecond pulse generation from a MXene mode-locked fiber laser. We have prepared the high-quality Ti_3C_2 T_x nanosheets via the etching method, and characterized their ultrafast dynamics and broadband nonlinear optical responses. The obvious intensity-and wavelength-dependent nonlinear responses have been observed and investigated. In addition, a highly stable femtosecond fiber laser with signal-to-noise ratio up to 70.7 dB and central wavelength of 1567.3 nm has been delivered. The study may provide some valuable design guidelines for the development of ultrafast, broadband nonlinear optical modulators, and open new avenues toward advanced photonic devices based on MXenes.
基金supported by the National Natural Science Foundation of China under grant Nos. 50772134 and 50802115the National Basic Research Program of China ("973 Program") under grant No. 2006CB600901
文摘Oxidation protective MoSi2-MosSi3/SiC multi-coatings for carbon/carbon composites were prepared by chemical vapor reaction and slurry-sintering method. The influence of preparation technology on the structure and phase composition of the coating was investigated by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS） and X-ray diffraction （XRD） analyses, and then their relationship was discussed. The results indicate that the Si/Mo ratio of the slurry and sintering processing were two main factors that significantly affected the structure and phase composition of the multi-coating. Appropriate sintering process and relatively high Si/Mo ratio were essential for preparing the multi-coating with dense structure and favorable phase composition. After being sintered at 1723 K for 2 h and with the Si/Mo ratio of the slurry being 4.5 （weight ratio）, a dense structure accompanied by favorable phase composition of the coating can be obtained. When heat treated at 2373 K for I h, this coating became more compact and continuous. Oxidation tests （performed at 1623 and 1823 K） demonstrated that both of these two obtained multi-coatings exhibited better anti-oxidation property than single layer SiC coating.
